Sticking with
http://www.bigfive.com
Step 1 is to go to
http://validator.w3.org and get the page to validate, that includes adding a DOCTYPE to it.
There are only 28 errors, but they will get in the way of fixing the page, especially the </p> without the opening
For the DOCTYPE I'd use one of the Strict ones. This will have an effect on the way IE renders the page see
http://www.alistapart.com/articles/doctype/ as a start.
Once you've got that done then it's a case of looking to see what other problems are in there.
In future I suggest to design for Firefox and fix for IE, it's much easier.